This invention relates to a programmable sequence controller, and more particularly to a programmable sequence controller from which it is possible to omit a tape reader for reading a paper tape into which a sequence program or the like has been punched.
Numerical control systems permit various mechanical elements in machine tools, robots and other devices to be controlled on the basis of instructions from a numerical control device which incorporates an operation panel. It is necessary in such numerical control systems to provide circuitry between the numerical control device (referred to as an NC hereinafter) and the machine in order to transmit the NC commands to each of the mechanical elements. This is conventionally accomplished by the provision of heavy current circuitry comprising a multiplicity of relay groups, the relays being actuated in accordance with the NC commands such as M-function instructions, S-function instructions and commands from the operation panel. The conventional arrangement, however, incorporates a numerical control system which is large in size, and necessitates a large number of relays in order to handle more complicated operations. Higher cost and a decline in reliability are the result.
A proposed system for improving upon the foregoing arrangement employs a programmable sequence controller to perform the function of the relays. With a programmable sequence controller the processing of signals between the NC and the machine is accomplished by way of the program, so that the problems of system size and operation complexity can be solved without a major increase in cost. Nevertheless, some increase in the cost and size of the system cannot be avoided with the conventional programmable sequence controller since the controller must be provided with its own program input means such as a tape reader.